Liquid transport device and liquid transport method

ABSTRACT

A liquid transport device includes a drive mechanism having a rotor rotating when transporting a liquid, and a detection section adapted to detect a rotational angle of the rotor, and power of the detection section is switched between an ON state and an OFF state in sync with switching between drive and halt of the drive mechanism. Such a liquid transport device driven by the rotation of a cam or the rotor can reduce the power consumption of an encoder.

BACKGROUND

1. Technical Field

The present invention relates to a liquid transport device and a liquidtransport method.

2. Related Art

As a liquid transport device for transporting a liquid, there has beenknown a micropump described in JP-A-2013-24185 (Document 1). In themicropump, there is disposed a plurality of fingers along a tube, and bya cam sequentially pushing the fingers, the tube is squeezed and thusthe liquid is transported. Further, there is disposed an encoder formeasuring the rotational angle of the cam or a rotor for rotationallydriving the cam.

In such a liquid transport device as described in Document 1, atransport operation and a halt operation of the liquid are performedrepeatedly in some cases. For example, in the case of using the liquidtransport device as an insulin injection device, there is repeated anoperation of sending an insulin solution for three seconds per minute,and stopping the liquid transport for the remaining 57 seconds. In suchan insulin injection device as described above, since there is a highrequirement for precisely controlling the transport amount of theinsulin, it is arranged that the rotational angle of the cam or therotor can be detected with high accuracy using an optical encoder.However, if the power of the light emitting section and the lightreceiving section of the optical encoder is always kept in the ON state,the power consumption in stopping the liquid transport operation iswasted.

Further, in such a liquid transport device as described in Document 1,in order to perform the liquid transport with accuracy, it is necessaryto detect the rotational angle of the cam with high accuracy using theencoder. In other words, it is necessary to, for example, transport acorrect amount of insulin within the period of three seconds in whichthe liquid transport operation is performed out of the period of oneminute. However, when repeatedly performing the liquid transportoperation and the halt operation, the position of the cam is shifted dueto the factor that an external force is applied in stopping the liquidtransport operation, or the detection position is varied due to theinfluence of a backlash of a rotation mechanism of the cam, and thus,the detection value by the encoder fluctuates to make it easy to causean error. Further, there is also a possibility that the detection valueof the encoder fluctuates due to the influence of noise and so on. Ifsuch a fluctuation occurs, the actual rotational angle of the cam or therotor becomes uncertain, and therefore, it becomes difficult totransport an accurate amount of liquid when resuming the liquidtransport operation in the halt state.

SUMMARY

An advantage of some aspects of the invention is to reduce the powerconsumption of the encoder in a liquid transport device driven byrotation of a rotor.

Another advantage of some aspects of the invention is to reduce thefluctuation of a detection value of an encoder in a liquid transportdevice driven by rotation of a rotor.

A principal aspect of the invention is directed to a liquid transportdevice including a drive mechanism having a rotor rotating whentransporting a liquid, and a detection section adapted to detect arotational angle of the rotor, wherein power of the detection section isswitched between an ON state and an OFF state in sync with switchingbetween drive and halt of the drive mechanism.

Other features of the invention will be apparent from the presentspecification and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is an overall perspective view of a liquid transport device.

FIG. 2 is an exploded view of the liquid transport device.

FIG. 3 is a cross-sectional view of the liquid transport device.

FIG. 4 is a see-through top view of the inside of the liquid transportdevice.

FIG. 5 is a briefing diagram of a pump section.

FIG. 6 is a block diagram for explaining detection sections and acontrol section of the liquid transport device.

FIG. 7 is a diagram for explaining a variety of detection sectionsprovided to a drive mechanism.

FIG. 8 is an explanatory diagram of a cam-side reflecting sectionprovided to a cam.

FIG. 9 is an explanatory diagram of a first rotor-side reflectingsections and a second rotor-side reflecting section provided to a rotor.

FIG. 10 is a diagram showing a relationship between signals CAM_Z,ROT_Z, ROT_A, and ROT_B.

FIG. 11 is a diagram for explaining a relationship between the signalsROT_A and ROT_B.

FIG. 12 is a side view for explaining an operation in detecting therotational angle of the rotor with the detection sections.

FIG. 13 is a diagram for explaining a circuit (an encoder circuit) foroutputting the output signal ROT_A.

FIG. 14 is a diagram for explaining a hysteresis characteristic.

FIG. 15 is a diagram for explaining a modified example of the encodercircuit.

FIG. 16 is a diagram showing the flow in changing the drive mechanismfrom a halt state to a drive state.

FIG. 17 is a diagram showing the flow in changing the drive mechanismfrom the drive state to the halt state.

FIG. 18 is a diagram for explaining power supply control in changing thedrive mechanism from the halt state to the drive state.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

The description of the present specification and the accompanyingdrawings will make at least following items apparent.

A liquid transport device includes a drive mechanism having a rotorrotating when transporting a liquid, and a detection section adapted todetect a rotational angle of the rotor, and power of the detectionsection is switched between an ON state and an OFF state in sync withswitching between drive and halt of the drive mechanism.

According to such a liquid transport device, since the detection sectionis powered OFF during the period in which the drive mechanism does notoperate, the power consumption of the detection section in performingthe liquid transport operation can be reduced. Further, by reducing thepower consumption of the detection section, the power consumption of thewhole of the liquid transport device can be reduced.

In such a liquid transport device as described above, it is preferablethat the detection section includes a light emitting section adapted toemit light, and a light receiving section adapted to receive the lightemitted, and power of the light emitting section is switched between theON state and the OFF state in sync with switching between the ON stateand the OFF state of power of the drive mechanism.

According to such a liquid transport device, the power consumption canbe reduced in the light emitting section having high energy consumptionamong the detection section in performing the liquid transportoperation. By reducing the power consumption of the light emittingsection, the power consumption of the whole of the liquid transportdevice can more significantly be reduced.

In such a liquid transport device as described above, it is preferablethat the detection section has an encoder circuit adapted to output anoutput signal having a predetermined level based on a detection value ofa rotational angle of the rotor, and power of the encoder circuit isswitched between the ON state and the OFF state in sync with switchingbetween the ON state and the OFF state of power of the drive mechanism.

According to such a liquid transport device, the power consumption inthe encoder circuit among the constituents of the detection section canbe reduced. Thus, in performing the liquid transport operation with theliquid transport device, the power consumption of the operation ofdetecting the rotational angle of the rotor can be reduced.

In such a liquid transport device as described above, it is preferablethat in starting drive of the drive mechanism, the power of the lightemitting section is set to the ON state, and then the power of theencoder circuit is set to the ON state, and in stopping drive of thedrive mechanism, the power of the encoder circuit is set to the OFFstate, and then the power of the light emitting section is set to theOFF state.

According to such a liquid transport device, even in the case ofperforming intermittent drive of repeating drive and halt of the drivemechanism, the power consumption in the detection section can be reducedwhile accurately controlling the liquid transport operation. In otherwords, it is possible to achieve both of the accurate liquid transportoperation and the reduction of the power consumption in the liquidtransport device.

In such a liquid transport device as described above, it is preferablethat the detection section includes an encoder adapted to detect arotational angle of the rotor, a comparator circuit adapted to comparethe detection value detected by the encoder and a predeterminedreference value with each other to output a signal having one of an Hlevel and an L level, and a reference value setting section adapted todetect the signal output to vary the reference value.

According to such a liquid transport device as described above, inperforming the liquid transport operation, it becomes possible tosuppress the fluctuation of the detection value of the encoder, and itbecomes possible to more accurately control the drive/halt operation ofthe drive mechanism. Therefore, it becomes possible to accuratelycontrol the timing of setting the power to the ON state in sync withdrive of the drive mechanism and the timing of setting the power to theOFF state in sync with the halt of the drive mechanism, and thus, it ispossible to reduce the power consumption in performing the liquidtransport operation (the intermittent drive) of repeating drive and haltin the liquid transport device.

In such a liquid transport device as described above, it is preferableto include a resetting section adapted to store a level of the signaloutput at a time point when the drive mechanism has stopped in a case ofperforming intermittent drive of repeating drive and halt of the drivemechanism, and apply a resetting voltage having a level corresponding toa level of the signal stored to the comparator circuit in driving thedrive mechanism again.

According to such a liquid transport device as described above, even inthe case in which the position of the cam or the rotor has been shifteddue to the influence of an external force while the drive mechanism isat rest, the rotation of the cam and so on can be controlled in the samestate as at the time of stopping drive in resuming drive of the drivemechanism. Therefore, it becomes possible to more accurately control thedrive/halt operation of the drive mechanism. Thus, it becomes possibleto more accurately control the timing of switching the power of thedetection section between the ON state and the OFF state, and it becomeseasy to further reduce the power consumption in the intermittent drivein the liquid transport device.

In such a liquid transport device as described above, it is preferablethat the comparator circuit includes a comparator adapted to compare alevel of an input voltage and a reference voltage with each other tooutput the signal having one of the H level and the L level, and theresetting section applies the resetting voltage to a terminal of thecomparator to which the input voltage is input.

According to such a liquid transport device as described above, byapplying the resetting voltage to the input voltage side of thecomparator, it becomes easy to reproduce the level of the output signal,which has been output when the drive mechanism has stopped, at the timeof resuming drive of the drive mechanism. Thus, it becomes possible tomore accurately control the drive/halt operation of the drive mechanism,and therefore, it becomes possible to accurately control the liquidtransport operation in the intermittent drive in the liquid transportdevice.

In such a liquid transport device as described above, it is preferablethat the comparator circuit includes a comparator adapted to compare alevel of an input voltage and a level of a reference voltage with eachother to output the signal having one of the H level and the L level,and the resetting section applies the resetting voltage to a terminal ofthe comparator to which the reference voltage is input.

According to such a liquid transport device as described above, byapplying the resetting voltage to the reference voltage input side ofthe comparator, it becomes easy to reproduce the level of the outputsignal, which has been output when the drive mechanism has stopped, atthe time of resuming drive of the drive mechanism. Thus, it becomespossible to more accurately control the drive/halt operation of thedrive mechanism, and therefore, it becomes possible to accuratelycontrol the liquid transport operation in the intermittent drive in theliquid transport device. Further, since it is possible to apply theresetting voltage to an arbitrary position between the output side andthe reference voltage input side of the comparator, the degree offreedom of circuit design increases, and it becomes possible tocompactly configure the liquid transport device.

In such a liquid transport device as described above, it is preferablethat the detection section includes a first encoder adapted to detectthe rotational angle of the rotor, a second encoder adapted to detectthe rotational angle of the rotor at a different position from aposition of the first encoder, and a control section adapted todetermine a rotational direction of the rotor based on whether the levelof the signal, which is output by the second encoder when the level ofthe signal output by the first encoder varies, is the H level or the Llevel.

According to such a liquid transport device, even in the case in whichthe rotational position of the rotor has been shifted due to theinfluence of the external force while the drive mechanism has been atrest, the direction in which the shift has occurred can be identified,and therefore, it becomes easy to correct the shift. Thus, in resumingdrive of the drive mechanism in the halt state, it becomes easy toperform the more accurate liquid transport operation.

In such a liquid transport device as described above, it is preferableto include a cam driven by the rotation of the rotor to therebytransport the liquid, a rotation detection encoder adapted to detect arotation reference position of at least one of the cam and the rotor, arotational angle detection encoder adapted to detect the rotationalangle of the rotor, and a control section adapted to detect a shiftamount between the rotation reference position of at least one of thecam and the rotor detected by the rotation detection encoder, and therotational angle of the rotor detected by the rotational angle detectionencoder, and correct the rotation reference position as much as theshift amount detected.

According to such a liquid transport device as described above, even inthe case in which the rotation reference position to be a reference indetecting the rotational angle of the rotor and so on has been shifted,the shift amount can periodically be detected, and therefore, bycorrecting the rotation reference position as much as an amountcorresponding to the shift amount, the detection accuracy of therotational angle can be enhanced. Thus, even in the case of repeatingdrive and halt in the liquid transport device, the accurate liquidtransport operation can be performed.

Further, there will become apparent a liquid transport method includingdetecting a rotational angle of a rotor rotating when transporting aliquid, and switching a power of a detection section adapted to detectthe rotational angle of the rotor between an ON state and an OFF statein sync with switching between drive and halt of a drive mechanismhaving the rotor.

A liquid transport device includes a drive mechanism having a rotorrotating when transporting a liquid, and an encoder adapted to detect arotational angle of the rotor, a comparator circuit adapted to comparethe detection value detected by the encoder and a predeterminedreference value with each other to output a signal having one of an Hlevel and an L level, and a reference value setting section adapted todetect the signal output to vary the reference value.

According to such a liquid transport device as described above, thefluctuation of the detection value of the encoder can be reduced due tothe hysteresis characteristic in detecting the rotational angle of therotor. By reducing the fluctuation of the detection value, it becomeseasy to correctly detect the rotational angle of the rotor, andtherefore, it becomes possible to accurately control the operation ofthe drive mechanism. Thus, the accurate liquid transport operation canbe realized in the liquid transport device.

In such a liquid transport device as described above, it is preferablethat the drive mechanism includes a piezoelectric actuator adapted tomake a vibrator element, which vibrates in accordance with a drivesignal applied to the vibrator element, have contact with the rotor torotate the rotor, and the piezoelectric actuator is biased so that anend portion of the vibrator element and an outer circumferential portionof the rotor have contact with each other in a state in which avibration orbit of the vibrator element and a rotational plane of therotor are in parallel to each other.

According to such a liquid transport device as described above, therotor is biased against the vibrator element in the drive section tothereby generate a force in a direction perpendicular to the rotationalplane of the rotor, and even in the case in which the optical pathlength of the rotary encoder is fluctuated, chattering in the detectionvalue can be suppressed. Therefore, in the liquid transport device fortransporting a liquid by rotating the rotor with a piezoelectricactuator, the liquid transport operation can accurately be performed.

In such a liquid transport device as described above, it is preferablethat there is included a cam rotationally driven by the rotation of therotor to thereby transport the liquid, the drive mechanism includes areduction section adapted to reduce revolution of the rotor and thentransmit the rotation of the rotor to the cam, and the detection sectiondetects a rotational angle of the reduction section.

According to such a liquid transport device as described above, therotational angle of the cam can correctly be detected. Specifically, bydetecting the rotational angle of the cam via a reduction mechanismdisposed at the position, at which the distance from the cam is short,and the influence of the backlash is small, it becomes easy to detectthe rotation operation of the cam in the period of transporting theliquid. Further, since the rotation amount of the reduction section withrespect to the rotation amount of the cam becomes large if the reductionratio in the reduction section is large, by detecting the rotationalangle of the reduction section, the resolution of the rotational angleof the cam increases, and the rotational angle of the cam can bedetected with high accuracy. Therefore, it becomes easy to accuratelydetect the liquid transport amount in performing the liquid transportoperation with the liquid transport device.

In such a liquid transport device as described above, it is preferablethat there is included a cam rotationally driven by the rotation of therotor to transport the liquid, the drive mechanism includes a reductionsection adapted to reduce revolution of the rotor and then transmit therotation of the rotor to the cam, and the detection section detects arotational angle of the cam.

According to such a liquid transport device as described above, therotational angle of the cam can correctly be detected. Specifically, bydirectly detecting the rotational angle of the cam using the detectionsection provided to the cam, it becomes easy to correctly detect theactual operation of the cam in the period of transporting the liquid.Further, by directly detecting the rotational angle of the cam, itbecomes easy to obtain the data, in which the influence of the backlashis hardly included, namely the data with little noise. Therefore, itbecomes easy to accurately detect the liquid transport amount inperforming the liquid transport operation with the liquid transportdevice.

In such a liquid transport device as described above, it is preferableto include a resetting section adapted to store a level of the signaloutput at a time point when the drive mechanism has stopped in a case ofperforming intermittent drive of repeating drive and halt of the drivemechanism, and apply a resetting voltage having a level corresponding toa level of the signal stored to a predetermined terminal of thecomparator circuit in driving the drive mechanism again.

According to such a liquid transport device as described above, even inthe case in which the position of the cam or the rotor has been shifteddue to the influence of an external force while the drive mechanism isat rest, the rotation of the cam and the rotor can be controlled in thesame state as at the time of stopping drive in resuming drive of thedrive mechanism. Thus, even in the case of performing the intermittentdrive of repeating drive and halt in the liquid transport device, theliquid transport amount can accurately be controlled.

Further, there will become apparent a liquid transport method includingdetecting a rotational angle of a rotor rotating when transporting aliquid, comparing a detection value detected and a predeterminedreference value with each other to output a signal having one of an Hlevel and an L level, and detecting the signal output to vary thereference value.

According to such a liquid transport method as described above, thefluctuation of the detection value of the rotational angle of the rotordetected by the encoder can be reduced due to the hysteresischaracteristic in detecting the rotational angle of the rotor. Byreducing the fluctuation of the detection value, it becomes easy tocorrectly detect the rotational angle of the rotor, and therefore, itbecomes possible to accurately control the operation of the drivemechanism. Therefore, the accurate liquid transportation can berealized.

Embodiment Liquid Transport Device

FIG. 1 is an overall perspective view of a liquid transport device 1.FIG. 2 is an exploded view of the liquid transport device 1. As shown inthe drawings, in some cases, the explanation is presented assuming thatthe side (living body side) to which the liquid transport device 1adheres is “downside,” and the opposite side is “upside.”

The liquid transport device 1 is a device for transporting a liquid. Theliquid transport device 1 is provided with a main body 10, a cartridge20, and a patch 30. The main body 10, the cartridge 20, and the patch 30can be separated as shown in FIG. 2, but are integrally assembled toeach other as shown in FIG. 1 when used. The liquid transport device 1is preferably used for periodically injecting a liquid (e.g., insulin)stored in the cartridge 20 with, for example, the patch 30 attached tothe living body. In the case in which the liquid stored in the cartridge20 is exhausted, the main body 10 and the patch 30 are continuously usedalthough the cartridge 20 is replaced.

Pump Section 5

FIG. 3 is a cross-sectional view of the liquid transport device 1. FIG.4 is a see-through top view of the inside of the liquid transport device1, and also shows a configuration of a pump section 5. FIG. 5 is abriefing diagram of the pump section 5.

The pump section 5 has a function as a pump for transporting the liquidstored in the cartridge 20, and is provided with a tube 21, a pluralityof fingers 22, a cam 11, and a drive mechanism 12.

The tube 21 is a pipe for transporting a liquid. The upstream side (theupstream side with reference to the transportation direction of theliquid) of the tube 21 communicates with a storage section 26 for theliquid in the cartridge 20. The tube 21 has such elasticity that thetube 21 is choked when being pressed by the fingers 22, and is restoredwhen the force from the fingers 22 is released. The tube 21 is disposedalong the inner surface of a tube guide wall 25 of the cartridge 20 soas to partially have a circular arc shape. The part of the tube 21having a circular arc shape is disposed between the inner surface of thetube guide wall 25 and the plurality of fingers 22. The center of thecircular arc of the tube 21 coincides with the rotational center of thecam 11.

Fingers 22 are members for choking the tube 21. The fingers 22 act in afollowing manner with a force applied from the cam 11. The fingers 22each have a shaft section having a rod-like shape and a pressing sectionhaving a flange shape, and forms a T shape. The shaft section having arod-like shape has contact with the cam 11, and the pressing sectionhaving a flange shape has contact with the tube 21. The fingers 22 areeach supported so as to be movable along the shaft direction.

The plurality of fingers 22 is disposed radially from the rotationalcenter of the cam 11 at regular intervals. The plurality of fingers 22is disposed between the cam 11 and the tube 21. Here, the seven fingers22 are disposed.

The cam 11 has projection sections 11A at a plurality of places (fourplaces in FIG. 5) on the outer circumference. The plurality of fingers22 is disposed on the outer circumference of the cam 11, and the tube 21is disposed on the outer side of the fingers 22. By the fingers 22 beingpressed by the projection sections 11A of the cam 11, the tube ischoked. When the fingers 22 disengage from the projection section 11A,the tube 21 is restored to the original shape due to the elastic forceof the tube 21. When the cam 11 rotates, the seven fingers 22 aresequentially pressed by the projection section 11A, and thus, the tube21 is choked sequentially from the upstream side in the transportationdirection. Thus, a peristaltic motion is caused in the tube 21, andthus, the liquid filling the inside is compressed by the tube 21 and isthus transported.

Drive Mechanism 12

The drive mechanism 12 is a mechanism for rotationally driving the cam11, and has a piezoelectric actuator 121, a rotor 122, and a reductiontransmission mechanism 123 as shown in FIG. 4.

The piezoelectric actuator 121 is an actuator for rotating the rotor 122using the vibration of piezoelectric elements. By applying a drivesignal to the piezoelectric elements bonded to the both sides of thevibrator element having a rectangular shape, the piezoelectric actuator121 vibrates the vibrator element. The end portion of the vibratorelement is disposed at the position at which the end portion can havecontact with the rotor 122. When the vibrator element vibrates, the endportion of the vibrator element vibrates so as to draw a predeterminedorbit such as an elliptical orbit or a figure-eight orbit, and byintermittently having contact with the rotor 122 in a part of thevibration orbit, the rotor 122 is driven rotationally. The piezoelectricactuator 121 is biased toward the rotor 122 with a pair of springs(spring members) so that the end portion of the vibrator element hascontact with the rotor 122. In other words, the piezoelectric actuator121 is biased so that the end portion of the vibrator element and theouter circumferential portion of the rotor 122 have contact with eachother in the state in which the vibration orbit of the vibrator elementand the rotational plane of the rotor 122 are parallel to each other.

The rotor 122 is a driven body rotated by the piezoelectric actuator121. The rotor 122 is provided with a rotor pinion constituting a partof the reduction transmission mechanism 123.

The reduction transmission mechanism 123 is a mechanism for transmittingthe rotation of the rotor 122 to the cam 11 at a predetermined reductionratio. The reduction transmission mechanism 123 is formed of a rotorpinion, a transmission wheel 123A, and a cam wheel (see FIG. 7). Therotor pinion is a pinion integrally attached to the rotor 122. Thetransmission wheel 123A has a main wheel engaged with the rotor pinionand a pinion engaged with the cam wheel, and has a function oftransmitting the rotational force of the rotor 122 to the cam 11. Thecam wheel is integrally attached to the cam 11, and is rotatablysupported together with the cam 11. It should be noted that thereduction ratio of the reduction transmission mechanism 123 is assumedhere to be 40. In other words, when the rotor 122 rotates onerevolution, it results that the cam 11 rotates 1/40 revolution.

It should be noted that among the tube 21, the plurality of fingers 22,the cam 11, and the drive mechanism 12 constituting the pump section 5,the cam 11 and the drive mechanism 12 are provided to the main body 10,and the tube 21 and the plurality of fingers 22 are provided to thecartridge 20. The main body 10 is also provided with detection sections40 for measuring the rotational angle of the cam 11 or the like, acontrol section 50 for performing control of the piezoelectric actuator121 and so on, and a battery 19 for supplying the piezoelectric actuator121 and so on with electrical power.

Detection Sections 40, Control Section 50

FIG. 6 is a block diagram for explaining detection sections 40 and acontrol section 50 of the liquid transport device 1. FIG. 7 is a diagramfor explaining the variety of detection sections 40 provided to thedrive mechanism 12.

The detection sections 40 include a cam rotation detection section 41for detecting the rotational state of the cam 11, and a first rotorrotation angle detection section 43, a second rotor rotation angledetection section 44, and a rotor rotation detection section 45 fordetecting the rotational state of the rotor 22. Here, the “rotationalstate” of the cam 11 or the rotor 22 denotes the rotation amount fromeach of rotation reference positions set respectively, and is detectedas the rotational angle of the cam 11 or the rotor 22.

The cam rotation detection section 41 is a rotary encoder provided witha photo reflector formed of a light emitting section 41A and a lightreceiving section 41B. The light emitting section 41A is a light source,which emits light for detecting the rotational angle of the detectionobject (here, the cam 11), and a light emitting diode, for example, isused. The light receiving section 41B is a light receiving section forreceiving the light, which has been emitted from the light emittingsection 41A, and then reflected by the detection object, and aphotodiode, for example, is used. In the present embodiment, the cam 11is provided with a cam-side reflecting section 111, the cam-sidereflecting section 111 reflects the light from the light emittingsection 41A, and the light receiving section 41B receives the light thusreflected. FIG. 8 is an explanatory diagram of the cam-side reflectingsection 111 provided to the cam 11. As described in FIG. 8, the singlecam-side reflecting section 111 is provided to the gear wheel section ofthe cam 11. It should be noted that the positional relationship of thecam-side reflecting section 111 with respect to the projection section11A is different by a product. The light receiving section 41B outputs avoltage signal corresponding to the light reception amount, and thedetection section 40 (the cam rotation detection section 41) outputs theoutput signal CAM_Z having an H level or an L level to the controlsection 50 based on the level of the voltage signal.

The first rotor rotation angle detection section 43 is a rotary encoderprovided with a light emitting section 43A and a light receiving section43B, and the second rotor rotation angle detection section 44 is arotary encoder provided with a light emitting section 44A and a lightreceiving section 44B. These sections each have substantially the samestructure as that of the cam rotation detection section 41. Further, therotor rotation detection section 45 is also a similar rotary encoder,and is provided with a light emitting section 45A and a light receivingsection 45B. The first rotor rotation angle detection section 43 and thesecond rotor rotation angle detection section 44 are disposed atpositions shifted by a predetermined rotational angle from each otherwith respect to the rotational direction of the rotor 122 (see FIG. 7).

The rotor 122 is provided with first rotor-side reflecting sections 124and a second rotor-side reflecting section 125. FIG. 9 is an explanatorydiagram of the first rotor-side reflecting sections 124 and the secondrotor-side reflecting section 125 provided to the rotor 122. As shown inFIG. 9, the 12 first rotor-side reflecting sections 124 are provided tothe rotor 122, and the reflecting sections are radially disposed withthe same distance and at regular intervals centered on the rotationalaxis of the rotor 122. In other words, the angle between the 2 firstrotor-side reflecting sections 124 adjacent to each other is 30 degrees.The light applied from the light emitting section 43A of the first rotorrotation angle detection section 43 and the light applied from the lightemitting section 44A of the second rotor rotation angle detectionsection 44 are reflected by the first rotor-side reflecting sections124, and are respectively received by the light receiving sections 43Band 44B. Then, the light receiving sections 43B and 44B output thevoltage signals corresponding to the light reception amounts, and thedetection sections 40 output the output signals ROT_A and ROT_B eachhaving the H level or the L level to the control section 50 based on thelevels of the voltage signals, respectively. The single secondrotor-side reflecting section 125 is formed on the inner side of thefirst rotor-side reflecting sections 124, namely on the rotational axisside of the rotor 22. The light applied from the light emitting section45A of the rotor rotation detection section 45 is reflected by thesecond rotor-side reflecting section 125, and is received by the lightreceiving section 45B. The light receiving section 45B outputs a voltagesignal corresponding to the light reception amount, and the detectionsection 40 outputs the output signal ROT_Z having the H level or the Llevel to the control section 50 based on the level of the voltagesignal.

It should be noted that the cam rotation detection section 41, the firstrotor rotation angle detection section 43, the second rotor rotationangle detection section 44, and the rotor rotation detection section 45are each not limited to a reflective optical sensor (so-called photoreflector), but can also be a transmissive optical sensor.

The control section 50 has a counter 51, a storage section 52, anarithmetic section 53, and a driver 54 as shown in FIG. 6. The counter51 counts the number of edges included in each of the output signalROT_A of the first rotor rotation angle detection section 43, and theoutput signal ROT_B of the second rotor rotation angle detection section44. The count value of the counter 51 represents the rotational angle ofthe rotor 122. Since the rotational angle of the rotor 122 and therotational angle of the cam 11 correspond to each other, the count valueof the counter 51 also represents the rotational angle of the cam 11.Further, the storage section 52 stores a program for the arithmeticsection 53 to drive the driver 54, and further stores the position onthe output signal ROT_A (ROT_B) corresponding to the original point ofthe pump. The arithmetic section 53 executes the program stored in thestorage section 52 to calculate the amount of the shift between thepositions of the rotor 122 and the cam 11 with respect to the originalpoint of the pump at the time point when the pump section 5 has stoppedand the positions of the rotor 122 and the cam 11 with respect to theoriginal point of the pump at present based on the count values (therotational angles of the cam 11 and the rotor 122) of the counter 51 andthe position on the output signal ROT_A (ROT_B) corresponding to theoriginal point of the pump. Further, if the shift has occurred, thearithmetic section 53 drives the driver 54 so as to reduce the influenceof the shift. The driver 54 outputs the drive signal to thepiezoelectric actuator 121 of the drive mechanism 12 with an instructionfrom the arithmetic section 53. Further, the counter 51 counts the edgesincluded in each of the output signal CAM_Z of the cam rotationdetection section 41, and the output signal ROT_Z of the rotor rotationdetection section 45 to thereby detect the number of revolutions of eachof the cam 11 and the rotor 122.

FIG. 10 is a diagram showing a relationship between the output signalsCAM_Z, ROT_Z, ROT_A, and ROT_B. As described above, the first rotationangle detection section 43 outputs the output signal ROT_A in accordancewith the amount of the reflected light received in the light receivingsection 43B. In the present embodiment, since the 12 first rotor-sidereflecting sections 124 are formed along the circumferential directionof the rotor 122 as shown in FIG. 9, the first rotor rotation angledetection section 43 outputs the signal ROT_A including 12 pulsedwaveforms every time the rotor 122 rotates one revolution. Similarly,the second rotor rotation angle detection section 44 outputs the signalROT_B including 12 pulsed waveforms.

Further, the rotor rotation detection section 45 outputs the outputsignal ROT_Z in accordance with the amount of the reflected lightreceived in the light receiving section 45B. Since the single secondrotor-side reflecting section 125 is formed along the circumferentialdirection of the rotor 122 as shown in FIG. 9, the rotor rotationdetection section 45 outputs the signal ROT_Z including one pulsedwaveform every time the rotor 122 rotates one revolution.

The cam rotation detection section 41 outputs the output signal CAM_Z inaccordance with the amount of the reflected light received in the lightreceiving section 41B. Since the single cam-side reflecting section 111is formed along the circumferential direction of the cam 11 as shown inFIG. 8, the cam rotation detection section 41 outputs the signal CAM_Zincluding one pulsed waveform every time the cam 11 rotates onerevolution.

As described above, since the rotor 122 rotates 40 revolutions while thecam 11 rotates one revolution, the number of pulses included in theoutput signal ROT_A of the first rotor rotation angle detection section43 corresponding to the rotor 122 in one cycle of the output signalCAM_Z of the cam rotation detection section 41 is obtained as 40×12=480.Therefore, defining each of the rising edge and the falling edge of thepulse in the signal ROT_A as one count, it results that 960 countsnumbered as 0 through 959 are measured in every revolution of the cam 11as shown in FIG. 10.

Further, by using the relationship between the output signals CAM_Z,ROT_Z, and the output signal ROT_A, the control section 50 can identifythe rotation reference position of the cam 11 (the rotor 122). Here, therotation reference position denotes a position used as a reference whendetecting the rotational angle of the cam 11 or the rotor 122. Bydetecting the moving distance from the rotation reference position, thecontrol section 50 can calculate the rotational angle (rotation amount)of the cam 11 or the rotor 122.

Although the details will be described later, since the drive state andthe halt state are repeated (intermittent drive) in the drive mechanism12 according to the present embodiment, the rotation reference positionof the cam 11 (the rotor 122) is shifted from the rotation referenceposition at the time of stoppage as much as roughly one or two pulses ofthe output signal ROT_A (the output signal ROT_B) in some cases due tothe influence of a backlash of the reduction transmission mechanism 123,outside forces or the like when restarting drive of the cam 11 (therotor 122) in the halt state. In such a case, by correcting the rotationreference position of the cam 11 (the rotor 122) as much as the shiftedpulses, it becomes possible to correctly perform the subsequent rotationcontrol of the cam 11 (the rotor 122). For example, in the case ofrestarting drive of the drive mechanism 12 in the halt state, thecontrol section 50 counts the number of pulses of the output signalROT_A (the output signal ROT_B) included in one cycle of the outputsignal CAM_Z or the output signal ROT_Z. Then, if the number of thepulses of the output signal ROT_A included in one revolution of the cam11 is one pulse smaller than 960 pulses, the correction is performed soas to set the position, at which the number of pulses is one pulsesmaller than that at the original rotation reference position, as anupdated rotation reference position. In contrast, if the number ofpulses is one pulse larger, the position at which the number of pulsesis one pulse larger than that at the original rotation referenceposition is set as the updated rotation reference position.

Further, the control section 50 can detect whether the rotationaldirection of the rotor 122 or the like is shifted in the normal rotationdirection or the reverse rotation direction based on the relationshipbetween the output signals ROT_A and ROT_B. Specifically, the controlsection 50 determines the direction in which the drive mechanism 12 hasrotated based on whether the level of the output signal ROT_B, which isdetected when the level of the output signal ROT_A is changed, is the Hlevel or the L level. FIG. 11 is a diagram for explaining therelationship between the signals ROT_A and ROT_B. As shown in FIG. 7,the first rotor rotation angle detection section 43 and the second rotorrotation angle detection section 44 are disposed at positions shifted bya predetermined amount from each other with respect to the rotationaldirection of the rotor 122. Therefore, the output signals ROT_A andROT_B, which are output in accordance with the light reflected by acertain reflecting section among the 12 first rotor-side reflectingsections 124 disposed, have a predetermined phase difference. In theexample shown in FIG. 11, the output signals ROT_A and ROT_B are outputin the state in which the phase of the output signal ROT_A and the phaseof the output signal ROT_B are shifted by 90° (π/2) from each other. Byusing the two signals having such a phase difference, the rotationalstate of the rotor 122 can be determined. In the liquid transport device1, although the rotor 122 moves in a period from when the liquidtransport operation by the pump section 5 is stopped to when the liquidtransport operation is resumed in some cases, the rotation controlamount in resuming the liquid transport operation varies in accordancewith whether the rotor 122 moves forward or backward in the rotationaldirection during the halt period of the pump section 5. In such a case,by respectively comparing the H/L levels of the output signals ROT_A andROT_B at the timing when the liquid transport operation by the pumpsection 5 is stopped with the H/L levels of the output signals ROT_A andROT_B at the timing when the liquid transport operation by the pumpsection 5 is resumed, it becomes possible to detect the rotationaldirection and the rotation amount of the rotor 122 during the periodfrom the stoppage of the pump section 5 to when the operation isresumed.

For example, at certain timing T1 shown in FIG. 11, the output signalROT_A shows the H level, and the output signal ROT_B shows the L level.If the output signal ROT_A shows the L level, and the output signalROT_B also shows the L level at the time point when a predeterminedmicro time has elapsed from this state (in the case of T2 shown in FIG.11), it is understood that the rotor 122 has been shifted in the reverserotation direction. In contrast, if the output signal ROT_A shows the Hlevel, and the output signal ROT_B also shows the H level (in the caseof T3 shown in FIG. 11), it is understood that the rotor 122 is shiftedin the normal rotation direction. As described above, by checking thelevel of the output signal ROT_B with respect to the change in the levelof the output signal ROT_A, whether the rotation having occurred is theforward rotation or the backward rotation can be determined.

Regarding Liquid Transport Operation

The liquid transport operation by the liquid transport device 1 isperformed by sequentially pressing the plurality of fingers 22 to causea peristaltic motion in the tube 21 while rotating the cam 11 asdescribed above to thereby move the liquid filling the inside of thetube 21. Therefore, in order to realize an accurate liquid transportoperation, it is required to accurately control the rotation amount ofthe cam 11. In particular, in the case of using the liquid transport 1as an insulin injection device and so on, accurate control is requiredfor the insulin injection amount and the injection timing. For example,in the insulin injection device, there is performed the intermittentdrive of performing the insulin injection operation for 3 seconds, andthen halting the injection operation for 57 seconds. Here, the maximuminjection amount of each injection is about 30 U (unit; 1 unit is equalto about 10 microliter).

In the case of performing such intermittent drive, noise is included inthe output signals ROT_A, ROT_B representing the rotational condition ofthe rotor 122 detected by the detection sections 40 in some cases. It isconceivable that, for example, due to the backlash of the rotor 122 andthe reduction transmission mechanism 123, the noise is generated whenrestarting the rotor 122 once stopped, or the electrical noise isincluded in the drive signal of the piezoelectric actuator 121 (the S/Nratio is decreased). Further, an influence of the noise generated due tothe structure of the drive mechanism 12 according to the presentembodiment is conceivable.

FIG. 12 is a side view for explaining the operation in detecting therotational angle of the rotor 122 with the detection sections 40.Although FIG. 12 shows the example of the case in which the rotationalangle of the rotor 122 with the first rotor rotation angle detectionsection 43 out of the detection sections 40, the configurations of otherdetection sections such as the second rotor rotation angle detectionsection 44 are essentially the same. As shown in FIG. 12, in the drivemechanism 12 according to the present embodiment, the vibrator elementprovided to the piezoelectric actuator 121 is biased by a spring fromthe lateral direction against the rotor 122. Then, the vibrator elementis driven to make the end portion of the vibrator element intermittentlyhave contact with the outer circumferential portion of the rotor 122 tothereby rotationally drive the rotor 122. On this occasion, the lightemitted from the light emitting section 43A of the first rotor rotationangle detection section 43 disposed on the lower part of the rotor 122is made to be reflected by the first rotor-side reflecting sections 124of the rotor 122, and is then received by the light receiving section43B. Then, the first rotor rotation angle detection section 43 outputsthe output signal ROT_A in accordance with the light reception amount ofthe received light.

In such a configuration, when rotating the rotor 122, there acts theforce of lifting the rotor 122 upward centered on the contact partbetween the rotor 122 and the vibrator element. In the presentspecification, the influence of such force is referred to as “pitch.” Incontrast, when the rotor 122 is stopped, since the force acting on therotor 122 becomes difficult to act, the “pitch” is difficult to occur.In the case in which the “pitch” has occurred, since the verticalposition of the rotor 122 is displaced as much as several throughseveral tens of micrometers compared to the case in which the “pitch”has not occurred, the optical path length of the first rotor rotationangle detection section 43 varies. As a result, the level of the voltagedetected by the light receiving section 43B varies, and there is apossibility that the potential, which is opposite to the potential to benormally output, is output. For example, although the first rotorrotation angle detection section 43 should normally output the outputsignal ROT_A having the H level, the output signal ROT_A having the Llevel is output in some cases. In other words, the influence of the“pitch” acts as the noise to inhibit the information related to theaccurate rotational position and so on of the rotor 122 from beingobtained, and there is a possibility that it becomes unachievable forthe control section 50 to perform the accurate liquid transportation.Further, there is a possibility that there occurs so-called chatteringin which the output signal ROT_A violently vibrates between the H leveland the L level due to the influence of the noise to make it difficultto detect the actual rotational angle of the rotor 122.

Improvement in Accuracy of Liquid Transport

In order to realize the accurate liquid transport operation using theliquid transport device 1, it is important to reduce the influence ofthe noise and so on generated when rotating or stopping the rotor 122.In the present embodiment, whether the output signal (e.g., the outputsignal ROT_A described above) at the time point when stopping the rotor122 is in the H level or in the L level is previously stored in thestorage section 52. Further, when rotationally driving the rotor 122again, the state of the output signal at the time of the stoppage is setto a circuit for outputting the output signal with reference to thestate of the output signal having been stored at the time of stoppage tothereby make it difficult to generate a difference in position betweenthe halt period of the rotor 122 and the time when resuming theoperation. Further, on this occasion, by providing a hysteresischaracteristic to the circuit for outputting the output signal, it isarranged that the rotational angle of the rotor 122 in performing theintermittent drive of the drive mechanism 12 can accurately be detected.

FIG. 13 is a diagram for explaining a circuit (hereinafter referred toas an encoder circuit 400) for outputting the output signal ROT_A.Although FIG. 13 shows an example of the case in which the output signalROT_A is output by the first rotor rotation angle detection section 43out of the detection sections 40, other detection sections such as thesecond rotor rotation angle detection section 44 have substantially thesame circuits. An operation of accurately outputting the output signalROT_A using the encoder circuit 400 will hereinafter be explained usingFIG. 13.

The encoder circuit 400 has the first rotor rotation angle detectionsection 43, a voltage follower 401, voltage follower resistors 402A,402B, a comparator circuit 410, a resetting circuit 420, an ALL POW SW,and a ROT_A SW.

Firstly, the ROT_A SW for setting the light emitting section 43A of thefirst rotor rotation angle detection section 43 to the light emissionstate is set to the ON state, and subsequently, the ALL POW SW forsetting the light receiving section 43B to a light receivable state isset to the ON state. It should be noted that by setting the ALL POW SWto the ON state, a reference voltage Vb described later is set to besupplied to a comparator 411. The light having been emitted from thelight emitting section 43A and then reflected by the first rotor-sidereflecting sections 124 of the rotor 122 is received by the lightreceiving section 43B. The light receiving section 43B outputs thevoltage having the level corresponding to the light intensity of thereflected light thus received, and then the voltage is input to aplus-terminal side of the voltage follower 401. The minus-terminal sideof the voltage follower 401 constitutes a feedback loop, and thus, thevoltage input to the voltage follower 401 is subject to impedanceconversion, and is then output. The voltage output from the voltagefollower 401 is input to a minus-terminal side of the comparator 411 ofthe comparator circuit 410 via a resistor 421 of the resetting circuit420.

Comparator Circuit 410

The comparator circuit 410 is a circuit for outputting a voltage signalhaving the H level or the L level in accordance with the level of thevoltage input thereto. The comparator circuit 410 according to thepresent embodiment has the comparator 411, reference voltage resistors412A, 412B, voltage divider resistors 413A, 413B, and hysteresisresistors 414A, 414B.

To the plus-side input terminal of the comparator 411, there is inputthe reference voltage Vb as a reference value, and an input voltage Vinis input to the minus-side input terminal. Further, the comparator 411outputs the voltage signal having the L level in the case in which theinput voltage Vin is equal to or higher than the reference voltage Vb(Vin≧Vb), and outputs the voltage signal having the H level in the casein which the input voltage Vin is lower than the reference voltage Vb(Vin<Vb). The voltage signal thus output is used as the signal ROT_A. Inthe present embodiment, the voltage having been supplied from the powersupply (3.3V) and then adjusted in the level via the reference voltageresistors 412A, 412B is input to the plus-side input terminal of thecomparator 411 as the reference voltage Vb. Meanwhile, the voltagedetected by the first rotor rotation angle detection section 43 is inputto the minus-side input terminal of the comparator 411 via the voltagefollower 401 and the resistor 421 as the input voltage Vin. For example,in the case in which the reference voltage Vb is equal to 2.5 V, if theinput voltage Vin is equal to or higher than 2.5 V, the output signalROT_A having the L level (e.g., 0 V) is output, and if the input voltageVin is lower than 2.5 V, the output signal ROT_A having the H level(e.g., 3.3 V) is output.

Here, in the case in which noise is included in the output voltage ofthe first rotor rotation angle detection section 43, there is apossibility that the level of the input voltage Vin vibrates in apredetermined range. For example, in the example described above, whenthe input voltage Vin vibrates up and down in the vicinity of thereference voltage Vb equal to 2.5V, the output signal ROT_A violentlyfluctuates (causes chattering) between the H level and the L level, andit becomes unachievable to figure out the accurate rotational conditionof the rotor 122. To deal with such a problem, in the comparator circuit410 according to the present embodiment, the hysteresis resistors 414A,414B are disposed to thereby provide a hysteresis characteristic to thecircuit to suppress the chattering in the output signal ROT_A.

The hysteresis resistors 414A, 414B are disposed between the output-sideterminal and the input-side terminal (the plus-side terminal) of thecomparator 411. In the case in which the voltage (the output signalROT_A) in the output-side terminal of the comparator 411 is in the Hlevel, the reference voltage Vb is changed to have a value Vbh higherthan the original value, and then input to the plus-side input terminalof the comparator 411 (Vbh>Vb) due to the relationship between thehysteresis resistors 414A, 414B and the reference voltage resistors412A, 412B, and the voltage divider resistors 413A, 413B. In contrast,in the case in which the output signal ROT_A is in the L level, thereference voltage Vb is changed to have a value Vbl lower than theoriginal value, and then input to the plus-side input terminal of thecomparator 411 (Vb>Vbl) due to the relationship between the referencevoltage resistors 412A, 412B, and the hysteresis resistors 414A, 414Band the voltage divider resistors 413A, 413B. Therefore, the referencevoltage resistors 412A, 412B, the voltage divider resistors 413A, 413B,and the hysteresis resistors 414A, 414B constitute a reference valuesetting section, and due to the operation of the reference value settingsection, the reference voltage Vb of the comparator 411 varies betweenVbl through Vbh.

FIG. 14 is a diagram for explaining the hysteresis characteristic. InFIG. 14, in the case in which the input voltage Vin is lower than thereference voltage Vb, since the H level is output as the output signalROT_A at the start, the reference voltage Vb rises to the value Vbh. Inthis case, when the input voltage Vin gradually rises, and then reachesa value equal to or higher than the raised reference voltage Vbh, theoutput signal ROT_A turns to the L level. In contrast, in the case inwhich the input voltage Vin is higher than the reference voltage Vb,since the L level is output as the output signal ROT_A at the start, thereference voltage Vb falls to the value Vbl. In this case, when theinput voltage Vin gradually falls, and then becomes lower than thelowered reference voltage Vbl, the output signal ROT_A turns to the Hlevel. Therefore, even if the input voltage Vin rises or falls in thevicinity of the reference voltage Vb due to the influence of noise andso on, the output signal ROT_A does not directly fluctuate between the Hlevel and the L level, and in the range of Vbl through Vbh, the outputsignal ROT_A becomes difficult to fluctuate. Further, in such a circuit,once the level of the output signal ROT_A is switched, the referencevoltage varies again, the output signal ROT_A becomes difficult tofluctuate even if the input voltage Vin rises or falls in some degree.For example, when the input voltage Vin gradually rises from a valuelower than the value Vb to become higher than the reference voltage Vbh,the reference voltage changes to Vbl. Therefore, even if the inputvoltage Vin vibrates in the vicinity of the level Vbh, the output signalROT_A is kept in the L level as long as the input voltage fails tobecome lower than the value Vbl.

In other words, in the encoder circuit 400 according to the presentembodiment, since the chattering in the output signal ROT_A can besuppressed by outputting the output signal ROT_A based on the hysteresischaracteristic, the fluctuation of the output value of the encoder isreduced, and it becomes easy to obtain an accurate output value with asmall influence of the noise and so on.

Resetting Circuit 420

As described above, in the case in which drive and stoppage of the drivemechanism 12 are repeated, due to the fact that the rotor 122 slightlymoves during the period from when the rotor 122 is stopped to when therotation is resumed, the detection value to be detected by the firstrotor rotation angle detection section 43 fluctuates in some cases. Inthe encoder circuit of the related art, since the rotation of the rotor122 is controlled based on the detection value at the time of resumingdrive, if the state in the period of stopping drive and the state at thetime of resuming drive are different from each other, it is difficult toaccurately control the liquid transport amount. In particular, in thecase of using the liquid transport device as an insulin injector, sinceit is required to inject an optimum amount of insulin to a patient, itis necessary to perform more accurate liquid transport control.Therefore, in the encoder circuit 400 according to the presentembodiment, the reference voltage value of the comparator 411 at thetime of resuming drive is reset by the resetting circuit 420 to therebysuppress the fluctuation of the detection value, and thus, it isarranged that the accurate output signal ROT_A can be output even in thecase in which the liquid transport device 1 is driven intermittently.

As shown in FIG. 13, the resetting circuit 420 has resistors 421 and422, and a resetting section 423. The resetting section 423 is a voltagesupply section for outputting a predetermined voltage value inaccordance with the level of the output signal at the time of stoppingdrive of the drive mechanism 12. Further, the resetting section 423 isalso a storage section for storing the output signal ROT_A output fromthe encoder circuit 400. In the case in which the liquid transportdevice 1 stops the liquid transport operation, the control section 50makes the resetting section 423 store whether the output signal ROT_Ahas been in the H level or in the L level at the time point when therotor 122, which has been rotationally driven, has stopped. Then, in thecase in which the liquid transport device 1 resumes the liquid transportoperation, the control section 50 outputs a resetting voltage, which hasa level corresponding to the opposite level to the level (the H level orthe L level) of the output signal ROT_A having been stored, to be inputto the minus-side input terminal of the comparator 411 via the resistor422. Thus, it results that the output signal ROT_A in the same state asthe state at the time of stopping the rotor 122 is output in thecomparator 411.

For example, it is assumed that the output signal ROT_A having the Hlevel has been output at the time point when the rotation of the rotor122 has stopped. In this case, the resetting section 423 inputs theresetting voltage corresponding to the L level to the minus-side inputterminal of the comparator 411 as the input voltage Vin. Then, since theinput voltage Vin becomes lower than the reference voltage Vb, thecomparator 411 outputs the output signal ROT_A having the H level. Itshould be noted that when the output signal ROT_A having the H level isoutput, the reference voltage Vb of the comparator 411 rises to thevalue Vbh, and in the subsequent operation of the rotor 122, the outputsignal ROT_A is output with reference to the value Vbh. Further, in thecase in which the output signal ROT_A having the L level has been outputat the time point when the rotation of the rotor 122 has stopped, theresetting section 423 inputs the resetting voltage corresponding to theH level to the comparator 411. Thus, the comparator 411 outputs theoutput signal ROT_A having the L level. As described above, by providingthe resetting circuit 420, the difference in the output signal betweenthe time point when drive of the drive mechanism 12 has been stopped andthe time point of resuming drive can be suppressed.

It should be noted that it is also possible to modify the configurationof the resetting circuit 420. FIG. 15 is a diagram for explaining amodified example of the encoder circuit 400. The encoder circuit 400according to the modified example is substantially the same as theencoder circuit 400 shown in FIG. 13, but is different therefrom in theconnection position and the operation of the resetting circuit 420. Inthe modified example, the resetting circuit 420 is disposed on theoutput side of the comparator 411. Then, by directly applying theresetting voltage having the same level as the voltage at the time ofstopping drive to the output side of the comparator 411, the value (theH level or the L level) of the output signal ROT_A is adjusted. In theexample shown in FIG. 15, the resetting section 423 stores the level ofthe output signal ROT_A at the time point when the rotor 122, which hasbeen rotationally driven, has stopped, and then, outputs the voltagehaving the same level at the time of resuming drive of the rotor 122.For example, in the case in which the output signal ROT_A having the Hlevel has been output at the time point when the rotation of the rotor122 has stopped, the resetting section 423 according to the modifiedexample applies the voltage corresponding to the H level to theoutput-side terminal of the comparator 411. Since the output signalROT_A becomes in the H level, the reference voltage of the comparator411 rises to the value Vbh, and in the subsequent operation of the rotor122, the output signal ROT_A is output with reference to the value Vbh.Thus, the difference in the output signal between the time point whendrive of the drive mechanism 12 has been stopped and the time point ofresuming drive can be suppressed. It should be noted that the positionat which the resetting circuit 420 is disposed in the modified exampleis not limited to the example shown in FIG. 15, but it is also possibleto dispose the resetting circuit 420 at any position between theoutput-side terminal and the plus-side input terminal of the comparator411.

Reduction of Energy Consumption

In the present embodiment, in order to accurately realize the liquidtransport operation, the rotational angles of the rotor 122 and the cam11 are detected using the optical sensors such as the first rotorrotation angle detection section 43 included in the detection sections40. In such optical sensors, it is necessary to continuously supply thelight emitting sections and the light receiving sections with theelectrical power when performing the detection. On the other hand, theintermittent drive of driving the device for 3 seconds and then haltingdrive for 57 seconds is assumed in the liquid transport device 1according to the present embodiment as described above, and it is notnecessary to keep the detection sections 40 operating when haltingdrive. This is because it becomes possible to inhibit the state of theoutput signal from changing between the period of halting drive and thetime point of resuming drive due to the comparator circuit 410, andtherefore, it is not necessary to monitor the shift of the rotationalangle of the rotor 122 and so on during the stoppage.

Therefore, the control section 50 performs the control so that thedetection sections 40 are supplied with the electrical power only in thepredetermined period of driving the drive mechanism 12, and areprevented from being supplied with the electrical power during theperiod in which the drive mechanism 12 is at rest to thereby reduce theenergy as much as an amount consumed by the detection sections 40 duringthe halt period. FIG. 16 is a diagram showing the flow in changing thedrive mechanism 12 from the halt state to the drive state. FIG. 17 is adiagram showing the flow in changing the drive mechanism 12 from thedrive state to the halt state. FIG. 18 is a diagram for explaining powersupply control in changing the drive mechanism 12 from the halt state tothe drive state.

In starting (resuming) drive of the drive mechanism 12 in the haltstate, a drive start signal as a logic signal for defining the start ofdrive is generated. It is also possible for the drive start signal toperiodically be generated under the management using a timer or thelike, or to be generated in response to an instruction (operation) forcommencement of injection performed by the user of the liquid transportdevice 1. In FIG. 16, by the control section 50 detecting the drivestart signal, a variety of control operations for driving the drivemechanism 12 are started (S101). When the control section 50 hasdetected the drive start signal, the control section 50 sets switches ofthe electrical power to be supplied to the detection sections 40 to theON state (S102). Here, the switch of the electrical power to be suppliedto the detection section 40 denotes a switch for supplying theelectrical power to the light emitting section of the optical sensor(rotary encoder), and corresponds to, for example, the ROT_A SW shown inFIG. 13, or a power switch of the light emitting section of anotherencoder. By setting the switches of the electrical power to the ONstate, the encoders such as the first rotor rotation angle detectionsection 43 start emitting the light. Subsequently, the control section50 performs (S103) setting of waiting time. The waiting time denotes thetime period from when setting the power switches of the light emittingsections of the encoders to the ON state to when the drive signal isapplied to the drive mechanism 12 (the rotor 122 and so on) to therebystart drive as shown in FIG. 18. In the present embodiment, thefluctuation of the detection value of the encoder is reduced byadjusting the level of the reference voltage to be input to thecomparator using the hysteresis characteristic in such an encodercircuit as shown in FIG. 13. Therefore, by waiting predetermined timeuntil the reference voltage stabilizes, it is arranged that therotational angles of the rotor 122 and so on can correctly be detected.After the waiting time has been set, the control section 50 performs(S104) setting of the reference voltage. The setting of the referencevoltage in starting drive of the drive mechanism 12 is performed usingsuch a resetting circuit as described above. Specifically, the controlsection 50 previously makes each of the resetting sections store whetherthe output signal (e.g., the ROT_A) of the encoder circuit at the timepoint when the drive mechanism 12 has been stopped is in the H level orin the L level, and then applies the voltage, which corresponds to theoutput signal having been stored, to each of the comparators to therebyperform the setting of the reference voltage.

Thus, it becomes possible to perform accurate drive control even in thecase of intermittently driving the drive mechanism 12. When the waitingtime has elapsed after the setting of the reference voltage is complete,the control section 50 sets (S105) the power switches of the encodercircuits to the ON state. The power switch of the encoder circuitdenotes a main power switch of the overall circuit for starting up thepiezoelectric actuator 121 and supplying the light receiving section ofthe optical sensor (rotary encoder) with the electrical power, andcorresponds to, for example, the ALL POW SW shown in FIG. 13. By settingthe power switches to the ON state, drive of the drive mechanism 12 isstarted. The detection values detected from the rotor 122 and the camrotationally driven are appropriately corrected in accordance with thehysteresis characteristic described above, and thus, the accuratecontrol is performed (S106).

In FIG. 17, in the case of stopping the drive mechanism 12, a drive haltsignal as a logic signal defining the halt of drive is generated, and isthen detected by the control section 50 to thereby start (S201) avariety of control operations for stopping the drive mechanism 12. Whenthe control section 50 has detected the drive halt signal, the controlsection 50 sets (S202) the power switch for driving the drive mechanism12 to the OFF state. Thus, the piezoelectric actuator 121 stops, and atthe same time, the detection sections 40 also stop the detection of therotational angles of the rotor 122 and so on. Subsequently, the controlsection 50 makes each of the resetting sections store (S203) whether theoutput signal (e.g., ROT_A) of the encoder circuit at the time pointwhen the drive mechanism 12 has been stopped is in the H level or in theL level. In resuming drive, the setting of the reference voltage isperformed (S104) using the data. After the output signal has beenstored, the control section 50 sets (S204) the waiting time. The waitingtime in the halt operation is a predetermined time period from when theelectrical power for driving the drive mechanism 12 is switched OFF towhen the drive mechanism 12 completely stops the operation. Then, afterthe waiting time has elapsed and the drive mechanism 12 has completelystopped, the control section 50 sets (S205) the switches of theelectrical power to be supplied to the detection sections 40 to the OFFstate. Thus, the halt operation of the drive mechanism 12 is complete.

In the present embodiment, by performing such control of the powersupply in starting drive of the drive mechanism 12 and in halting driveof the drive mechanism 12, the power consumption in the detectionsections 40 can be reduced. For example, as shown in FIG. 18, the timingat which the encoder is powered ON in starting drive is the timingslightly earlier than the timing of actually starting up thepiezoelectric actuator 121, specifically the timing earlier as much asthe waiting time, and the encoder is powered OFF in the period beforethe timing. Further, the timing at which the encoder is powered OFF instopping drive is the timing slightly later than the timing at which thepiezoelectric actuator 121 actually stops, specifically the timing lateras much as the waiting time. In other words, the power of the detectionsections 40 is set to the ON state before and after the timings betweenwhich the drive mechanism 12 is driven, and is set to the OFF state atother timings. Further, the power of the encoder is switched between theON state and the OFF state in sync with the timing at which the power ofthe drive mechanism 12 is switched between the ON state and the OFFstate. Therefore, in the intermittent drive of driving the drivemechanism 12 for only 3 seconds per minute as described above, theperiod in which the power of the detection sections 40 is in the ONstate is short, while the period in which the power is in the OFF stateis long. Thus, the power consumption of the detection sections(encoders) can be reduced. In particular, the power consumption in thelight emitting sections of the encoders having high power consumptioncan be reduced.

Other Issues

The embodiment described above is for facilitating understanding of theinvention, but not for providing limited interpretations of theinvention. It is obvious that the invention can be modified or improvedwithin the scope and the spirit thereof, and includes equivalentsthereof.

Regarding Detection Sections

Although in the embodiment described above, the rotor 122 of the drivemechanism 12 is provided with the rotary encoders (the first rotorrotation angle detection section 43, the second rotor rotation angledetection section 44, and the rotor rotation detection section 45), andthe rotational angle of the rotor 122 is detected using these encoders,it is also possible to dispose the rotary encoders at other positions.For example, it is also possible to arrange that the transmission wheel123A of the reduction transmission mechanism 123 is provided with arotary encoder similar to the first rotor rotation angle detectionsection 43 to detect the rotational angle of the transmission wheel123A. Similarly, it is also possible to arrange that the cam 11 isprovided with a rotary encoder similar to the first rotor rotation angledetection section 43 to directly detect the rotational angle of the cam11. By detecting the rotational angle at the position near to the cam11, it becomes difficult for the influence of the backlash and so on tobe included, and further, it becomes easy to detect the actual operationperformed when the projection sections 11A of the cam 11 press thefingers. It should be noted that since the revolution of the cam 11 isreduced at a predetermined reduction ratio with respect to therevolution of the rotor 122, by detecting the rotational angle of therotor 122, the data with higher resolution can be detected.

Regarding Pump Section

Although in the above description of the embodiments, there is explainedthe example of using a so-called tube pump, which transports the liquidin the tube by compressing the tube with a plurality of fingers, as thepump section of the liquid transport device, the configuration of thepump section is not limited to this example. It is also possible to useother pumps capable of transporting a liquid with an action of a camsuch as a screw pump for transporting a liquid in an axial direction byrotating a screw, or a plunger pump, which converts rotation of a caminto a motion of a plunger, and transporting a liquid using a reciprocalmotion of the plunger.

The entire disclosure of Japanese Patent Application Nos. 2014-122132,filed Jun. 13, 2014 and 2014-122133, filed Jun. 13, 2014 are expresslyincorporated by reference herein.

What is claimed is:
 1. A liquid transport device, comprising: a drivemechanism having a rotor rotating when transporting a liquid; and adetection section adapted to detect a rotational angle of the rotor,wherein power of the detection section is switched between an ON stateand an OFF state in sync with switching between drive and halt of thedrive mechanism.
 2. The liquid transport device according to claim 1,wherein the detection section includes a light emitting section adaptedto emit light, and a light receiving section adapted to receive thelight emitted, and power of the light emitting section is switchedbetween the ON state and the OFF state in sync with switching betweenthe ON state and the OFF state of power of the drive mechanism.
 3. Theliquid transport device according to claim 2, wherein the detectionsection has an encoder circuit adapted to output an output signal havinga predetermined level based on a detection value of a rotational angleof the rotor, and power of the encoder circuit is switched between theON state and the OFF state in sync with the switching between the ONstate and the OFF state of the power of the drive mechanism.
 4. Theliquid transport device according to claim 3, wherein in starting driveof the drive mechanism, the power of the light emitting section is setto the ON state, and then the power of the encoder circuit is set to theON state, and in stopping drive of the drive mechanism, the power of theencoder circuit is set to the OFF state, and then the power of the lightemitting section is set to the OFF state.
 5. The liquid transport deviceaccording to claim 1, wherein the detection section includes an encoderadapted to detect a rotational angle of the rotor, a comparator circuitadapted to compare the detection value detected by the encoder and apredetermined reference value with each other to output a signal havingone of an H level and an L level, and a reference value setting sectionadapted to detect the signal output to vary the reference value.
 6. Theliquid transport device according to claim 5, further comprising: aresetting section adapted to store a level of the signal output at atime point when the drive mechanism has stopped in a case of performingintermittent drive of repeating drive and halt of the drive mechanism,and apply a resetting voltage having a level corresponding to a level ofthe signal stored to the comparator circuit in driving the drivemechanism again.
 7. The liquid transport device according to claim 6,wherein the comparator circuit includes a comparator adapted to comparea level of an input voltage and a reference voltage with each other tooutput the signal having one of the H level and the L level, and theresetting section applies the resetting voltage to a terminal of thecomparator to which the input voltage is input.
 8. The liquid transportdevice according to claim 6, wherein the comparator circuit includes acomparator adapted to compare a level of an input voltage and areference voltage with each other to output the signal having one of theH level and the L level, and the resetting section applies the resettingvoltage to a terminal of the comparator to which the reference voltageis input.
 9. The liquid transport device according to claim 1, whereinthe detection section includes a first encoder adapted to detect therotational angle of the rotor, a second encoder adapted to detect therotational angle of the rotor at a different position from a position ofthe first encoder, and a control section adapted to determine arotational direction of the rotor based on whether the level of thesignal, which is output by the second encoder when the level of thesignal output by the first encoder varies, is the H level or the Llevel.
 10. The liquid transport device according to claim 1, furthercomprising: a cam driven by the rotation of the rotor to therebytransport the liquid; a rotation detection encoder adapted to detect arotation reference position of at least one of the cam and the rotor; arotational angle detection encoder adapted to detect the rotationalangle of the rotor; and a control section adapted to detect a shiftamount between the rotation reference position of at least one of thecam and the rotor detected by the rotation detection encoder, and therotational angle of the rotor detected by the rotational angle detectionencoder, and correct the rotation reference position as much as theshift amount detected.
 11. A liquid transport device, comprising: adrive mechanism having a rotor rotating when transporting a liquid; anencoder adapted to detect a rotational angle of the rotor; a comparatorcircuit adapted to compare the detection value detected by the encoderand a predetermined reference value with each other to output a signalhaving one of an H level and an L level; and a reference value settingsection adapted to detect the signal output to vary the reference value.12. The liquid transport device according to claim 11, wherein the drivemechanism includes a piezoelectric actuator adapted to make a vibratorelement, which vibrates in accordance with a drive signal applied to thevibrator element, have contact with the rotor to rotate the rotor, andthe piezoelectric actuator is biased so that an end portion of thevibrator element and an outer circumferential portion of the rotor havecontact with each other in a state in which a vibration orbit of thevibrator element and a rotational plane of the rotor are in parallel toeach other.
 13. The liquid transport device according to claim 11,further comprising: a cam rotationally driven by the rotation of therotor to thereby transport the liquid, wherein the drive mechanismincludes a reduction section adapted to reduce revolution of the rotorand then transmit the rotation of the rotor to the cam, and thedetection section detects a rotational angle of the reduction section.14. The liquid transport device according to claim 11, furthercomprising: a cam rotationally driven by the rotation of the rotor totransport the liquid, wherein the drive mechanism includes a reductionsection adapted to reduce revolution of the rotor and then transmit therotation of the rotor to the cam, and the detection section detects arotational angle of the cam.
 15. The liquid transport device accordingto claim 11, further comprising: a resetting section adapted to store alevel of the signal output at a time point when the drive mechanism hasstopped in a case of performing intermittent drive of repeating driveand halt of the drive mechanism, and apply a resetting voltage having alevel corresponding to a level of the signal stored to a predeterminedterminal of the comparator circuit in driving the drive mechanism again.16. A liquid transport method, comprising: detecting a rotational angleof a rotor rotating when transporting a liquid; and switching a power ofa detection section adapted to detect the rotational angle of the rotorbetween an ON state and an OFF state in sync with switching betweendrive and halt of a drive mechanism having the rotor.
 17. The liquidtransport method according to claim 16, further comprising: comparing adetection value detected and a predetermined reference value with eachother to output a signal having one of an H level and an L level; anddetecting the signal output to vary the reference value.